RUI: Contribution of Retinal Melatonin to Circulating Melatonin and its Importance in Metamorphosis

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This study will examine the ocular secretion of melatonin and the role of this melatonin in amphibian metamorphosis. The function of the vertebrate eye is not restricted to vision. Information about the environmental lighting cycle is conveyed to the circadian system via the eye and, in many nonmammalian vertebrates, the retina in the eye contributes melatonin to the circulation. Little is known about the extent of ocular melatonin secretion in amphibians. The technique of opthalmectomy will be used to determine the relative contribution of the eye to blood melatonin at different developmental stages in anuran tadpoles, as well as the relationships between retinal melatonin, thyroid hormones, and metamorphosis. This project will also examine light/dark cycle influences on circulating retinal melatonin, the association between retinal melatonin secretion and the diel rhythms in circulating melatonin and thyroxine, and whether a compensatory increase in melatonin production occurs after unilateral or bilateral opthalmectomy in an effort to maintain blood melatonin levels. These studies should improve our understanding of the role of melatonin in development and its relationship to photoperiodic influences on metamorphosis. The findings of this research might have significance as well to the study of hormone interactions and the role of melatonin in vertebrates in general. Moreover, these results may contribute to a better understanding of the environmental factors that affect declining amphibian populations. This project will be carried out with undergraduate students, to develop their competence and experience in research and to upgrade their career aspirations. A postdoctoral fellow who intends to seek a career in college teaching will also collaborate for one year to acquire experience in combining teaching and research at the college level. Thus, the project will contribute substantially to the National Science Foundation's objective of encouraging the integration of research into undergraduate programs and to advance discovery while promoting teaching, training, and learning.